Spot-type disc brake with a spring assembly for a brake lining

ABSTRACT

The present invention relates to a spot-type disc brake ( 1 ) with a brake housing ( 3 ) straddling a brake disc, with at least one brake lining ( 5, 6 ) that is arranged in the brake housing ( 3 ) so as to be slidable in the actuating direction and cooperates tribologically with the brake disc upon brake application, with at least one actuating device ( 4 ) arranged in the brake housing ( 3 ) to apply an actuating force to the brake lining ( 5 ), and with a spring assembly for the active adjustment of a clearance between the brake lining ( 5 ) and the brake disc after brake application. To simplify the configuration of the spring assembly, the spring assembly comprises exactly one spring ( 8, 18, 25, 31, 33 ) which is secured detachably in the spot-type disc brake ( 1 ) and is supported on the brake lining ( 5 ), on the one hand, and on the brake housing ( 3 ), on the other hand. A spring ( 8, 18, 25, 31, 33 ) of this type is arranged advantageously symmetrically within the brake housing ( 3 ) to prevent an undesirable inclined positioning of the brake linings.

[0001] The present invention relates to a spot-type disc brake with aspring assembly for the active adjustment of a clearance between a brakelining and a brake disc. A brake assembly of this type ensures that abrake lining is sufficiently lifted from the brake disc after brakeapplication is terminated.

[0002] DE 31 30 185 A1 discloses a disc brake with resetting springs ofthis type. The disc brake includes two resetting springs spaced in acircumferential direction and abutting with free spring legs on brakelinings arranged on either side of the brake disc. The brake linings arelifted from the brake disc after a brake operation due to the spreadingeffect of the spring legs. The springs are compressed between a brakeholder, a brake caliper and the brake linings in a first assembly. Theresetting springs are anchored only insufficiently in the disc brake sothat the resetting springs may easily be detached or get lost,especially when exposed to vibrations. In a second design, the resettingsprings are screwed to the disc brake. However, this necessitates anundesirable additional fastening means for each resetting spring. Inaddition, the use of two resetting springs basically involves the riskthat in the event of failure of one of the resetting springs there willoccur an inclined position of a brake lining which impairs functioning.

[0003] In view of the above, an object of the present invention is todisclose a spot-type disc brake with a spring assembly for the clearanceadjustment at one brake lining, which overcomes the shortcomings knownfrom the state of the art and, in addition, is easy to handle.

[0004] This object of the present invention is achieved by a spot-typedisc brake with a spring assembly according to patent claim 1.Accordingly, the spot-type disc brake comprises a brake housingstraddling a brake disc, with at least one brake lining that is arrangedin the brake housing so as to be slidable in the actuating direction andcooperates tribologically with the brake disc upon brake application. Atleast one actuating device to apply an actuating force to the brakelining is incorporated in the brake housing. To adjust a clearancebetween the brake lining and the brake disc upon termination of brakeapplication, the spot-type disc brake includes a spring assembly whichcomprises exactly one spring that is secured detachably to the spot-typedisc brake and is supported on the brake lining, on the one hand, and onthe brake housing, on the other hand. In particular the detachableattachment of the spring on a brake housing permits an especially simplemanipulation of the subassembly composed of brake housing, brake lining,and spring. Also, the spring is easy to mount and dismount.

[0005] An advantageous embodiment of the spot-type disc brake isachieved in that the spring extends substantially in the central planeof the brake housing with respect to the circumferential direction ofthe brake disc. Thus, an undesirable inclined positioning of the brakelining is avoided even in the extremely unlikely case of failure of thespring. In any case, the general braking function will not be impaired,not even when such a failure occurs.

[0006] A preferred variation of the spot-type disc brake is achievedwhen the spring is supported on a brake lining which directly cooperateswith at least one actuating device. This relates to spot-type discbrakes both in a fixed-type caliper and a floating-caliper construction,with a floating-caliper disc brake including a corresponding actuatingdevice only on one side of the brake disc. The action of the springdirected to the brake lining close to the actuating device has aparticularly positive effect on the clearance adjustment.

[0007] To facilitate the ability of mounting and dismounting of thespring, it may be provided that the spring with a first end portion isinserted into an accommodation recess at the brake lining. The endportion of the spring is fixed within the accommodation recess so as toprevent the end portion from slipping out of the accommodation recess.Above all in arrangements of the spot-type disc brake wherein two ormore actuating devices apply a brake force to the brake lining, it isappropriate that the first end portion of the spring is supported in acircumferential direction between two actuating devices on the brakelining. This achieves a symmetrical application of the spring force tothe brake lining and prevents an inclined positioning of brake linings.

[0008] In an expedient embodiment, the spring is configured as a tensionspring that is suspended with a second end portion on the brake housing.A tension spring of this type is a standard component permittinglow-cost application in the spring assembly of the present invention.The tension spring is preferably made of helical wire and suspended witha second end portion in a brake housing bore, for example. According toan alternative variation, the spring may of course also be designed as acompression spring which is detachably fastened on the brake housing.

[0009] Another favorable spring variation is achieved because the springis configured as a spiral leg spring which is detachably fastened with asecond end portion on the brake housing and acts as a bending spring.Above all, such a leg spring necessitates little mounting space and canbe adapted flexibly to any respective installation specifications bysimple shaping measures at its free ends. More particularly, the springlegs are configured in conformity with the preset supporting points onthe brake housing or on the brake lining. It is suitable above all inthis connection that at least one spring portion is shaped at the springand supported on the brake housing in a circumferential direction. Thisimproves anchoring of the spring on the brake housing, and lateraltilting of the spring with respect to the circumferential direction isprevented.

[0010] Further suitable detail features of the present invention can betaken from the embodiments in the Figures and will be explained indetail hereinbelow.

[0011] In the drawings,

[0012]FIG. 1 shows two views of a spot-type disc brake with a springassembly of the present invention for clearance adjustment comprising atension spring.

[0013]FIG. 2 shows two views of a spot-type disc brake with a leg springfor clearance adjustment.

[0014]FIG. 3 shows two partial views of an improved spring assembly witha second design of the leg spring.

[0015]FIG. 4 is a partial view of a spring assembly with a third designof the leg spring.

[0016]FIG. 5 shows two views of a spot-type disc brake with anotherdesign of the spring assembly.

[0017] The spot-type disc brake 1 of an automotive vehicle shown in theFigures comprises a brake holder 2 mounted fast on the vehicle and abrake housing 3 slidably mounted on the brake holder 2. Moreparticularly, housing 3 is designed as a brake caliper straddling abrake disc (not shown). On one side of the brake disc, the brake housing3 includes at least one actuating device 4 for the application of brakelinings 5, 6 arranged on either side of the brake disc. During a brakeapplication, a first brake lining 5 is applied by the actuating device 4directly and a second brake lining 6 is pressed due to an axial shift ofthe brake housing 3 indirectly against the brake disc. In the Figures,embodiments of the brake housing with two actuating devices 4 are shownwhich are designed as a hydraulic piston-and-cylinder unit. It is ofcourse also possible to use pneumatically, electrically, or mechanicallyacting actuating devices 4. Besides, the embodiment of the spot-typedisc brake 1 according to the present invention is not limited to thearrangement of a defined number of actuating devices 4 in the brakehousing 3. The brake linings 5, 6 arranged on either side of the brakedisc are straddled by the brake housing 3 in a caliper-like fashion andare slidably supported on holding arms 7 projecting over the brake discfor the purpose of transmitting circumferential brake forces. Further,the brake linings 5, 6 are detachably connected to the actuating device4, on the one hand, and to the axially outward leg of the brake housing,on the other hand.

[0018] To adjust a sufficient clearance between the brake linings 5, 6and the brake disc after a braking operation or brake application, thereis provision of a spring assembly which actively lifts the brake lining5 from the brake disc after brake application. This prevents a frictioncontact between the brake lining 5 and the brake disc outside thebraking phases and the resulting development of residual brake torques.This also prevents an uneven abrasion of material from the brake disc,frequently in the type of local brake washouts. In the embodiments ofthe spot-type disc brake according to the Figures, the spring assemblyacts on one side on the first brake lining S which is directly coupledto at least one actuating device 4. The second axially outward brakelining 6 is usually anchored axially on the brake housing 3 and liftedfrom the brake disc during continued travel, either due to an axialshift of the brake housing 3 or uneven rotations of the brake disc,e.g., brake disc eccentricity. As an alternative, it is also possible tohave the spring assembly act also on brake linings 5, 6 on both sides ofthe brake disc. For the symmetrical spring load on the brake lining 5,it is advisable to arrange the spring assembly with respect to thecircumferential direction 9 of the brake disc substantially in thecentral plane 10 or plane of symmetry of the brake housing 3, thatmeans, between the two actuating devices 4.

[0019]FIG. 1 shows a first design of the spring assembly with a woundtension spring 8 which, with a first spring end 11, is attached to thebrake lining 5 and, with a second spring end 12, is attached to thebrake housing 3. The first spring end 11 is preferably hooked detachablyat a shackle 13 on the brake lining 5, the said shackle being shaped onthe side of the brake lining 5 remote from the friction lining 14.Especially, the shackle 13 is secured to the back side of a carrierplate 15, the front side of which carries the friction lining 14. Thesecond spring end 12 is hooked into a bore 16 or other indentation inthe brake housing 3 and thus fixed in a detachable manner. However,still other appropriate fastening means are possible for the detachablefixation of the two spring ends 11, 12. The first spring end 11 issecured to the brake lining 5 so that the point of force application ofthe tension spring 8 on the brake lining 5 radially overlaps the forcecontact area of the actuating devices 4 on the brake lining 5. Theresult is that a spring force is exerted on the brake lining 5 whichactively lifts the said from the brake disc after brake application.Additionally, the point of force application is chosen so as to preventan inclined positioning of the brake lining 5 with respect to thefriction surface of the brake disc. Further, the tension spring 8ensures the clearance-free abutment of the brake lining 5 on theactuating device 4, for example, a brake piston. The actual spiral-typewound tension spring 8 abuts in a protected fashion on the brake housing3 in an indentation 17 between the actuating devices 4. Consequently,the tension spring does not straddle the brake disc and is henceunaffected by the brake disc rotation. Similar to the design as atension spring 8, a compression spring is also possible for theadjustment of a clearance.

[0020]FIG. 2 shows a second embodiment of the spring assembly for theclearance adjustment with a bending spring that is configured as a woundleg spring 18 that straddles the brake disc. As has already beendescribed hereinabove, the leg spring 18 is arranged substantially inthe central plane 10 of the brake housing 3 to preclude an unsymmetricalspring load on the brake lining 5. This prevents an undesirable inclinedpositioning of the brake lining 5. In detail, the leg spring 18 isarranged in a recess 19 between two bridge portions 20 of the brakehousing 3. With its first leg 21, the leg spring 18 is suspended on ashackle 23 fastened at the brake lining 5. To this end, the first leg 21includes at its free end appropriate bent spring portions 24 to permitease of mounting the spring leg 21 at the shackle 23, on the one hand,and to prevent the spring leg 21 from slipping out of the shackle 23, onthe other hand. The second leg 22 of the leg spring 18 is supportedwithin the recess 19 on the brake housing 3. As mentioned before, thebrake lining 5 is centrally acted upon by spring force also in this caseso that an undesirable inclined positioning of brake linings will notoccur. In this arrangement, the spring force points away from the brakedisc.

[0021]FIG. 3 shows in two views an embodiment of the spring assembly forthe clearance adjustment with an improved leg spring 25. The first leg21 of the leg spring 25 is suspended with free, bent spring portions 24in the shackle 23 of the brake lining according to the embodiment ofFIG. 2. On the other hand, the second leg 22 is supported in acircumferential direction 9 on the brake housing 3 by means of twospring arms 26 which extend opposedly in a circumferential direction.Preferably, the opposing spring arms 26 are symmetrically supported inthe recess 19. The support of the spring arms 26 within the recess 19prevents a tilting movement of the leg spring 25 in a circumferentialdirection 9. This loss-proof hold of the leg spring 25 in the brakehousing 3 is augmented by the support of the second leg 22 on the brakehousing 3. To this end, two groove-shaped indentations 27, 28 are shapedradially on the top side or bottom side of the brake housing 3 adjacentto the recess 19 at brake housing 3. The indentations 27, 28 are shapedinto the brake housing 3 e.g. by way of a machining operation. Theindentations may also be shaped during casting of the brake housing 3which is especially favorable for the manufacture. The second spring leg22 abuts in these indentations 27, 28 with matingly configured fasteningportions 29, 30, especially under spring bias. This improves theaccurate positioning and hold of the leg spring 25 on the brake housing3.

[0022]FIG. 4 illustrates another variation of a leg spring 31 with asimplified support of the second spring leg 22 on the brake housing 3.Only one indentation 27 is shaped at the radial bottom side of the brakehousing 3 in which the associated fastening portion 29 of the leg spring31 abuts. The support by way of the spring arms 26 which is lateral in acircumferential direction is maintained. In total, the leg spring 31compared to the embodiment of FIG. 3 can be designed in a simplifiedfashion with respect to the necessary bending deformations. As analternative, the fastening portion 29′ of the leg spring 31 can also besuspended into a bore 32 at the brake housing 3 in order to safelyattach the leg spring 31 to the brake housing 3.

[0023]FIG. 5 illustrates in two views another variation of the springassembly, wherein the support of the leg spring 33 in a circumferentialdirection 9 is improved once more. The spring arms 26 extending in acircumferential direction 9 are arranged in a pocket 34 adjacent to therecess 19 and designed on the radial top side of the brake housing 3.This renders it possible to fix the leg spring 33 not only in acircumferential direction 9 but also in a radially accurate positioningon the brake housing 3. In a way that is favorable under aspects ofmanufacturing technology, a pocket 34 of this type may also be shapedalready during casting fabrication of the housing 3, with the resultthat there is no more need for machining. Further attachment of the legspring 33 on the brake lining 5 or on the brake housing 3 is carried outin conformity with the other embodiments.

[0024] The actual active spring (8, 18, 25, 33) for the adjustment ofclearances is favorably made of spring wire and, accordingly, can beadapted extremely flexibly to any respective installation specificationsby means of simple bending operations. In addition, the spring (8, 18,25, 33) can be made of sheet metal or any other suitable springmaterial.

[0025] The detachable securement of the spring (8, 18, 25, 33) on thebrake lining 5 is carried out at an appropriately designed accommodationrecess, for example, a shackle (13, 23) according to the Figures. Anaccommodation recess of this type can be shaped directly to the brakelining 5 or the carrier plate 15, or can be designed on a holdingelement 35, roughly as in FIGS. 2 to 5. In these Figures, the holdingelement 35 is composed of a sheet-metal strip 35 which is fastened tothe carrier plate 15 and on which the shackle 23 is provided.

[0026] Basically, a spring assembly of the present invention for theadjustment of clearances was described by way of the Figures only in theexample of spot-type disc brakes 1 of the floating-caliper type ofconstruction. Of course, a spring assembly of this type permits beingused also in fixed-caliper spot-type disc brakes.

1. Spot-type disc brake (1) with a brake housing (3) straddling a brakedisc, with at least one brake lining (5, 6) that is arranged in thebrake housing (3) so as to be slidable in the actuating direction andcooperates tribologically with the brake disc upon brake application,with at least one actuating device (4) arranged in the brake housing (3)to apply an actuating force to the brake lining (5), and with a springassembly to adjust a clearance between the brake lining (5) and thebrake disc, characterized in that the spring assembly comprises exactlyone spring (8, 18, 25, 31, 33) which is secured detachably in thespot-type disc brake (1) and is supported on the brake lining (5), onthe one hand, and on the brake housing (3), on the other hand. 2.Spot-type disc brake as claimed in claim 1, characterized in that thespring (8, 18, 25, 31, 33) extends substantially in the central plane(10) of the brake housing (3) with respect to the circumferentialdirection (9) of the brake disc.
 3. Spot-type disc brake as claimed inany one of the preceding claims, characterized in that the spring (8,18, 25, 31, 33) is supported on a brake lining (5) which is coupled toat least one actuating device (4).
 4. Spot-type disc brake as claimed inany one of the preceding claims, characterized in that the spring (8,18, 25, 31, 33) with a first end portion (11, 21, 24) is inserted intoan accommodation recess (13, 23) at the brake lining (5).
 5. Spot-typedisc brake as claimed in any one of the preceding claims, characterizedin that the first end portion (11, 21, 24) is supported on the brakelining (5) in a circumferential direction (9) between two actuatingdevices (4).
 6. Spot-type disc brake as claimed in any one of thepreceding claims, characterized in that the spring is configured as atension spring (8) that is suspended with a second end portion (12) onthe brake housing (3).
 7. Spot-type disc brake as claimed in any one ofthe preceding claims, characterized in that the spring is designed as acompression spring which is detachably fastened with a second portion tothe brake housing (3).
 8. Spot-type disc brake as claimed in any one ofthe preceding claims, characterized in that the spring is configured asa leg spring (18, 25, 31, 33) which is detachably fastened with a secondportion (22, 29, 30) on the brake housing (3).
 9. Spot-type disc brakeas claimed in any one of the preceding claims, characterized in that atleast one spring portion (26) is shaped at the spring and is supportedon the brake housing (3) in a circumferential direction (9).